In constructing a liquid crystal display panel of large size, a circuit for driving pixels of a liquid crystal display panel also needs to be large. Hence, there is generally employed a method wherein a circuit board having a driving circuit for the panel is connected with the panel. With this method, to construct a larger-size liquid crystal display device by combining multiple panels, there is a need to bend the circuit board, toward the back side of the panels. In this case, the electrode terminals of the panels are connected with the terminal of the circuit board by means of TABs having a flexible property.
FIG. 3 is a schematic perspective view showing an example of a liquid display device wherein a liquid crystal display panel 12 is connected with a circuit board 11 by means of TABs 13, and the circuit board 11 is bent so as to be perpendicular to the panel 12. FIGS. 4 and 5 are enlarged explanatory views showing a connecting portion of the TAB. The TAB 13 is provided with an in opening 13a at one end thereof. Thereby, bare wires the TAB is connected with the circuit terminal portion of the circuit board 11 by means of solder 14. Further, the back side of film portion of the TAB 13 is bonded to the front side of the circuit board 11 with a double coated adhesive tape 15 at a side edge portion of the circuit board 11 so as to prevent pivotal movement of the circuit board 11 or the TAB 13 about the connecting portion connected by the solder, and disconnection in the connecting portion.
When the above structure is employed, however, the double coated adhesive tape 15 must be provided. Accordingly, the number of parts needed is increased. Further, the number of production steps is increased accompanying with a rise in production cost. Moreover, if the TAB 13 erroneously comes into contact with the reverse side of the adhesive tape 15 when the wires in the connection opening 13a are to be positioned to coincide with the circuit terminal portion of the circuit board 11, the film part of the TAB 13 is fixed by the adhesive force of the tape 15. Therefore, it is likely difficult to correct the position of the TAB. Such positioning before soldering requires a high precision since the wires to be connected with the connecting portion of the circuit board have a width of, for example, about 0.8 mm and an interval of about 0.4 mm between adjacent ones. Thus, the wires in the connection opening 13a cannot be precisely positioned due to the adhesive tape.
It should be noted that the TAB 13 is provided with an IC 16 so that signals are processed. Therefore, the liquid crystal display panel has 80 pieces of connecting wires, while the circuit board has 20 pieces of connecting wires.